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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - [compiler-rt][lli][halfType] lli segfaults while executing half type."
href="https://bugs.llvm.org/show_bug.cgi?id=48213">48213</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>[compiler-rt][lli][halfType] lli segfaults while executing half type.
</td>
</tr>
<tr>
<th>Product</th>
<td>compiler-rt
</td>
</tr>
<tr>
<th>Version</th>
<td>11.0
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>builtins
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>vikram.tarikere@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>Created <span class=""><a href="attachment.cgi?id=24180" name="attach_24180" title="IR containing half type - fails to JIT-execute.">attachment 24180</a> <a href="attachment.cgi?id=24180&action=edit" title="IR containing half type - fails to JIT-execute.">[details]</a></span>
IR containing half type - fails to JIT-execute.
The attached bitcode file (addHalf.ll) contains half types (adds 1.0 and 2.0 to
return 3.0) and it segfaults while executing with lli. I think lli fails to
find the right rtlibs because if I compile with llc and link with compiler-rt,
then it executes successfully.
$llc addHalf.ll
$clang addHalf.s --rtlib=compiler-rt // I need to link with compiler-rt due
to references for __gnu_h2f_ieee from half type conversions.
$./a.out
3.000000
Now, if I try to JIT-execute:
$lli addHalf.ll
PLEASE submit a bug report to <a href="https://bugs.llvm.org/">https://bugs.llvm.org/</a> and include the crash
backtrace.
Stack dump:
0. Program arguments: lli addHalf.ll
#0 0x00007f7e210929f0 llvm::sys::PrintStackTrace(llvm::raw_ostream&)
/local-ssd/vtariker/llvm/llvm-project/llvm/lib/Support/Unix/Signals.inc:564:0
#1 0x00007f7e21092a83 PrintStackTraceSignalHandler(void*)
/local-ssd/vtariker/llvm/llvm-project/llvm/lib/Support/Unix/Signals.inc:625:0
#2 0x00007f7e21090b2e llvm::sys::RunSignalHandlers()
/local-ssd/vtariker/llvm/llvm-project/llvm/lib/Support/Signals.cpp:68:0
#3 0x00007f7e21092433 SignalHandler(int)
/local-ssd/vtariker/llvm/llvm-project/llvm/lib/Support/Unix/Signals.inc:406:0
#4 0x00007f7e1e56c0c0 __restore_rt
(/lib/x86_64-linux-gnu/libpthread.so.0+0x110c0)
Segmentation fault
$
I have built the compiler-rt library. Maybe I need to tell lli to pick the
compiler-rt libs (just like in the llc case). If so, how do I do that?
A quick debug revealed that it segfaults at
lib/ExecutionEngine/MCJIT/MCJIT.cpp::runFunction() at line 583.
I used the below C-code to generate .ll and then edited it to convert single to
half type:
$cat addHalf.c
#include <stdio.h>
__attribute__((noinline)) float addHalf(float a, float b) {
return a + b;
}
int main() {
float a, b;
float ans;
a = 1.0;
b = 2.0;
ans = addHalf(a, b);
printf("%f\n", ans);
return 0;
}
$clang -emit-llvm addHalf.c -O0 -S -o addHalfO0.ll
$opt -mem2reg -instnamer addHalfO0.ll -S -o addHalf_single.ll // Edited
addHalf_single.ll to get the attached addHalf.ll.</pre>
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